Beyonce channelled Janet Jackson's Rhythm Nation look for her trick-or-treat day attire, which she unveiled at a Power 1051.1 Powerhouse event in New York on Thursday night (30Oct14), while her daughter Blue Ivy donned a Michael Jackson-inspired costume, complete with a mini red military jacket, black fedora, matching sunglasses and white gloves.

Perry and Allen also got a jump on the spookiest day of the year by attending actress Kate Hudson's Thursday night party as a Flaming Hot Cheeto snack and a midriff-baring gynaecologist, respectively.

Allen's surgeon donned scrubs, a stethoscope and a name badge that read 'Dr. Luke' - a nod to top hitmaker and producer Lukasz Gottwald.

Meanwhile, Swift posted a shot of herself dressed up like a mystical "pegacorn" - a flying unicorn - on Friday morning (31Oct14). She added the caption, "Cause, darling I'm a nightmare dressed like a PEGACORN. #HappyHalloween!"

Madonna's ex-husband Guy Ritchie and their son Rocco also dressed up for a Halloween party in London - the father and son went as Breaking Bad characters Walter White and Jesse Pinkman, and comedienne Ellen DeGeneres opened her Halloween TV special as George Clooney's new bride Amal.

Carrying a blow-up dummy with Clooney's face pasted on the head, DeGeneres greeted her studio audience and said, "Happy Halloween! You can probably tell who I am. I'm Amal, the luckiest woman in the world, Mrs. George Clooney."

The lesbian star, who hosted the 2014 Oscars, then quipped, "I like Halloween because it's the one time of year you can dress up however you want, and pretend you're someone you'd never be in real life. For me, that's married to a man."

She was joined on the show by Harry Potter star Daniel Radcliffe, who came dressed as Star Wars character Boba Fett and explained he had never been trick-or-treating.

He said, "It's kind of catching on now (in England), but when I was a kid it was really not big, for whatever reason. I've never been trick-or-treating in my life, which is a fact that sort of amazes a lot of people and I think I'm maybe missing out a little bit."

Australian pop star Kylie Minogue also got into the Halloween spirit ahead of her Friday night gig in Kaunas, Lithuania by donning skeletal Day of the Dead face paint for the show's soundcheck. She posted a creepy picture of herself on Twitter.com.